Unibody lubricator with externally threaded nipple

ABSTRACT

A lubricator for receiving a plunger is provided. The lubricator has a bore, a first end having a well head connection, a second end having a stem connection, and a plurality of ports, including a catcher port and flow ports. The flow ports are externally threaded nipples that extend radially beyond the outer surface of body of the lubricator.

FIELD OF THE INVENTION

The invention relates to a plunger lubricator.

BACKGROUND

During fluid production operations, a plunger lift system is sometimes used when pressure within a wellbore is insufficient to cause fluid to rise naturally. In a plunger lift system, a plunger serves as a mechanical interface between lift gas below the plunger and produced fluid above the plunger. When sufficient lift gas from the reservoir collects below the plunger to provide buoyant lift to the plunger and produced fluid above the plunger, the fluid and plunger are elevated in the wellbore to the surface. At the surface, a lubricator is used to absorb the kinetic energy of the plunger and to recover the plunger from the wellbore. The lubricator has fluid flow ports where produced fluids above the plunger maybe fed to, for instance, a pipeline or collection system.

Canadian patent no. 2,635,993 discloses a plunger lubricator housing, which comprises an elongated tubular body made from a single piece of material. The body has a first end, a second end, an outer surface, an inner surface that defines a plunger receiving interior bore, and radial ports which provide fluid communication between the interior bore and the outer surface. Each of the radial ports 43 has a threaded coupling that is inset from the outer surface of the body 40. FIG. 6 illustrates an example of a radial port 43 having a threaded coupling 41 inset in the body 40, which is shown to be connected to the external threads 42 of a fitting 44. As fluid flows out of port 43 (and the direction of fluid flow is indicated by an arrow “F”), the fluid may cause erosion in an area 42 near the junction of threaded coupling 41 and fitting 44 because the presence of the fitting 44 disrupts the flow path within port 43 as the fluid has to change directions to flow around the fitting.

SUMMARY OF INVENTION

The invention disclosed herein provides for a plunger lubricator.

In accordance with one aspect of the present invention, there is provided a lubricator for receiving a plunger comprising: an outer surface; an inner surface defining a bore; a well head connection at a first end for connecting a well head; a stem connection at a second end for connecting a stem; at least one flow port for connecting a flow line, the at least one flow port being an externally threaded nipple that extends radially outwardly from the outer surface; and a catcher port for catching a plunger.

In accordance with another aspect of the present invention, there is provided a method for connecting a plunger lubricator to a flow line fitting having external threads, comprising: providing an externally threaded nipple that extends radially outwardly from an outer surface of the lubricator; threadedly connecting the externally threaded nipple to a first end of an internally threaded collar; and threadedly connecting a second end of the internally threaded collar to the external threads of the flow line fitting.

BRIEF DESCRIPTION OF THE DRAWINGS

Drawings are included for the purpose of illustrating certain aspects of the invention. Such drawings and the description thereof are intended to facilitate understanding and should not be considered limiting of the invention. Drawings are included, in which:

FIG. 1 A is a perspective view of a first side of a lubricator;

FIG. 1B is a perspective view of a second side of the lubricator;

FIG. 2 is an elevation view of the second side of the lubricator;

FIG. 3 is a cross-sectional view of the lubricator along the line “A-A” in FIG. 2;

FIG. 4 is an elevation view of the first side of the lubricator;

FIG. 5 is an enlarged view of the part marked “B” of the lubricator in FIG. 3;

FIG. 6 is a cross-sectional view of a port of a prior art lubricator; and

FIG. 7 is a cross-sectional view of a flow port of the present lubricator.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

Referring to FIGS. 1A, 1B, and 2 to 5, a lubricator 10 comprises an outer surface 14 and a bore 18 defined by an inner surface 12. Bore 18 is for receiving a plunger (not shown). Lubricator 10 also includes a well head connection 20 at a first end for connecting to a well head (not shown), and a stem connection 24 at a second end for connecting to a stem (not shown). Lubricator 10 may be formed by forging, machining bar stock, casting, or a combination of known manufacturing methods.

Lubricator 10 further includes flow ports 28 for connecting to flow lines (not shown). In one embodiment, flow ports 28 are externally threaded nipples 29 that extend radially beyond outer surface 14. Lubricator 10 may also be provided with other ports 30, which may be used for attaching gauges or sensors, or for injecting chemicals. Lubricator 10 may also comprise a catcher port 34 to catch a plunger at the top of its stroke. Ports 30 and 34 may be external nipples that extend radially outwardly from outer surface 14. In one embodiment, ports 28, 30, and 34 are machined into lubricator 10. In another embodiment, ports 28, 30, and 34 are formed by creating apertures in the body of lubricator 10 and then integrating separate components to the circumference of the apertures, for example, by attaching threadolets by welding. In one embodiment, lubricator 10 includes an equipment attachment which may be used for attaching a sensor to indicate the arrival of a plunger. In another embodiment, other components, such as lifting eyelets, are welded or otherwise attached to lubricator 10.

In one embodiment, lubricator 10 is constructed from a single piece of material as described hereinafter. A single piece of material is machined, forged, or casted to form bore 18 and outer surface 14. The material may be any metal meeting proper specifications for strength, temperature rating, ductility, durability, corrosion resistance, capability of being welded, worked or machined, typically a steel, and preferably 4130 or 4140 carbon steel. Well head connection 20 is machined at the first end, and stem connection 24 is machined at the second end. In one embodiment, outer surface 14 may be machined to form ports 28, 30 and 34. In another embodiment, apertures are created in the body of lubricator 10 and separate threadolet components may be welded to the circumference of the apertures to form ports 28, 30, and 34. In a further embodiment, outer surface 14 is machined to have an increased thickness at various points along the length of the lubricator 10 such that the lubricator 10 may have increased thickness about ports 28, 30 and 34, or at other locations.

Referring to FIGS. 6 and 7, in contrast to the prior art radial port 40 having an inset threaded coupling 41, flow port 28 of lubricator 10 is an externally threaded nipple 29. In one embodiment, nipple 29 is connected to fitting 44 by a collar 46. Collar 46 may have internal threads that allow collar 46 to mate with the external threads of nipple 29 and fitting 44. Connecting nipple 29 and fitting 44 using collar 46 may minimize erosion of the inner surface of flow port 28 and fitting 44. Further, collar 46 may provide additional reinforcement by increasing the wall thickness at the joint between nipple 29 and fitting 44. In a further embodiment, a compressible washer 48 is disposed inside collar 46, between the adjacent ends of nipple 29 and fitting 44. Compressible washer 48 may act i) to protect the threads on collar 46; ii) to seal the joint between nipple 29 and fitting 44; and/or iii) as a lock-washer, which exerts longitudinal force to increase thread-to-thread friction between the collar's threads' side-slopes and the mating surfaces in the threads of nipple 29 and fitting 44.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article “a” or “an” is not intended to mean “one and only one” unless specifically so stated, but rather “one or more”. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are know or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. 

1. A lubricator for receiving a plunger comprising: an outer surface; an inner surface defining a bore; a well head connection at a first end for connecting a well head; a stem connection at a second end for connecting a stem; at least one flow port for connecting a flow line, the at least one flow port being an externally threaded nipple that extends radially outwardly from the outer surface; and a catcher port for catching a plunger.
 2. The lubricator of claim 1, further comprising a supplementary port for attaching gauges or sensors, or for injecting chemicals.
 3. The lubricator of claim 1, wherein the externally threaded nipple is a threadolet attached to an aperture that allows fluid to flow between the inner surface and the outer surface.
 4. The lubricator of claim 3, wherein the threadolet is attached by welding.
 5. The lubricator of claim 1, wherein the lubricator is formed by forging, machining, casting, or a combination thereof.
 6. The lubricator of claim 1, further comprising lifting eyelets.
 7. A method for connecting a plunger lubricator to a flow line fitting having external threads, comprising: providing an externally threaded nipple that extends radially outwardly from an outer surface of the lubricator; threadedly connecting the externally threaded nipple to a first end of an internally threaded collar; and threadedly connecting a second end of the internally threaded collar to the external threads of the flow line fitting.
 8. The method of claim 7, further comprising disposing a compressible washer inside the collar, between the externally threaded nipple and the flow line fitting. 